Spark-plug.



J. G. ANDERSON.

SPARK PLUG.

APPLICATION FILED MAILZO, 1909.

936,507. Patented Oct. 12,1909.

.UNITED STATES PATENT OFFICE.

James C. ammnson, or wasnme'ron, ms'rmc'r or comniiam.

SPARK-PLUG.

'- Specification of Letters Patent.

Patented Oct. 12, 1909.

' Application filed March 20, 1909. Serial No. 484,725.

To all whom it may concern:

Be it known that I, JAMES C. ANDERSON, a citizen of the United States,residing at WVashington, in the District of Columbia, have inventedcertain new and useful Improvements in Spark-Plugs; and I do hereby dhire the followin to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which'itappertains to make and use the same.

My invention relates to certain new and useful nnprovements. inspark-plugs, particularly of that type shown and described in -LettersPatent granted to me July 7 1903,

No. 732,812, in which the central electrode.

and easing are insulated by glass, welded to the electrode and casing.

My present invention has for its object to produce. a spark-plug whichshall be simple and economical of construction, and which shall bedevoid of the possibility of short-circuiting by reason of the presenceof carbon, oil or moisture deposited on, or between the electrodes.

lVith these ends in view, my invention consists in the details ofconstruction and arrangement hereinafter more fully set .forth.

In'order that those skilled in the art to which my invention appertainsmay know how to make my improved spark-plug and fully appreciate itsadvantages, I will pro-' oeed'to describe the same, referring bynumorals to the accompanying. drawing in which: c

Figure l is'a central longitudinal section of a spark-plug embodying thefeatures of my invention; Fig. 2 is an' inner; endview of the same; Fig.3 isa view similar to Fig. 1', and illustrating "a modification of thesame. Fig. *li's a'detail section of the construction shown at Fig. 1,and on enlarged scale to more fully illustrate the relation of theelectrodes andthe insulation; and

Fig. 5 is a similar enlarged sectional view :of the modifiedconstruct-ion shown at Fig. 3. ike

Similar reference numerals indicate parts in the severalfigures ofthedrawing'.

, 1,' represents the casing, and 2, the positive '50.

stereos insulated from one another by a body'ofglass, 3, welded tothecasing and the electrode as. fully set forth in theLetters Patenthereinbefore referred to.

J f-Th shelhlllj clearly shown in Figs. 4

' integral head which constitutes the negative 5, terminates at itsinnerend in a thin chamber in a vertical direction.

electrode 4. This head or negative electrode is formed with an opening5, the edge of which surrounds, and is at sparking distance from thepositive electrode 2, and also with a series of openings 6, between ,thecentral opening 5 and the periphery of the shell.

The insulatin lass 3 enters these 0 enin 's 6, and terminates flush withthe outer surface of the electrode, while it terminates at the localityof the opening 5, coincident with the inner surface of said electrode,as shown at Fig. 4, or with the outer surface, as shown at Fig. 5, asmay be preferred. The perforati'ons or openings 6 in the negativeelectrode are provided in order that the flash of the explosionwithinthe explosive chamber of an engine may be readi y observed from without.

In Fig. 3, I have shown a modification in which the head, or negativeelectrode 4, is of concave'd form, which may be desirable when the sparkplug enters. the explosive In this modified construction, it will beseen that the positive electrode where it passes through the centralopening 5 projects slightly .beyond the outer exposed surface of thenegative electrode, and hence should any lubricating oil or moistureaccumulate upon the exposed endof the positive electrode, or

between itand the negative electrode, it will be led to gravitate towardthe extremity of theelectrode, and sparking will then, take place abovesuch obstruction and until the heat generated will evaporate or dispelthe same.

In either of the constructions shown, it will be seen that the negativeelectrode surrounds the positive electrode and is at all oints at theminimum sparking distance mm the positive electrode, and that theinsulating body at the particular locality at which the sparking takesplace is coextensive only with the sparking gap or are be"- tween theelectrodes.

and customary to make the superficial area of the exposed surface-of theinsulating material as great as poss1ble within the-limits wall ofv theshell, again ,by extending the central electrode and the surrounding in-At this point I wish to state that it'has heretofore been desirablesulation beyond the inner extremity of the shell, or by forming a.cavity in' theinsulabe depositedupon the surface of the insulacleansingor Wiping action of such spark, and expels or dissipates any shortcircuitouter surface of the negative electrode, the

tion and between it and the central electrode, thus as stated securingthe greatest possible distance from one extremity to the,other of 5 theexposed surface of the insulation. My invention on the contrary involvesthe generic feature of reducing the distance over the exposedsurface ofthe insulation to the minimum and at the locality at which the sparkingoccurs in order that any short cirj cuitingbody which may be depositedupon the surface lof the insulating material will be dispelled orevaporated by the heat generated by the sparl As shown in the drawing,the insulating material 3 which is welded with the shell 1, and positiveelectrode 2, presents a surface at the particular locality at which thesparking must take place, coextensive with the sparking gap between theelectrodes, and this sparking gap is preferably of minimum extent inorder that the spark may be of the greatest intensity, in order thatitm'ay overcome and dispel the comparatively feeble conductivity of anyshort circuiting substance which may be deposited in the gapor arebetween the electrodes, and hence operate to expel or remove the same,and thus preserve continuous and uninterrupted sparking.

When the insulating body 3 extends only to, and in the same plane'withthe inner surface of the negative electrode 4, the sparking takes placewithin the circumferential space between it and the positive electrode2, and hence the surface of the insulating material coincident with theinner surface of the negative electrode is subjected to the ing medium.Likewise if the insulating material extends to, and coincident with thespark will jump from the positive to the negative electrode and over theinsulating material, and in a similar manner dissipate any shortcircuiting material which might tion.

I wish it to be understood that'the generic and underlying feature of myinvention resides in the fact that the insulating'material at theparticular locality at which the sparking takes place is coextensiveonly with i the sparking gap or are between the two electrodes, or inother words, the two eleci trodes are so arranged that one completely 3surrounds the other at uniform and minimum sparking distance, and thatthe entire circumferential area of the insulation between the electrodesis such, that the flash from the central electrode to the surround- Iing electrode simultaneously and uniformly traverses the entire surfaceof the insulating material 3, and consequently the entire surface ofthis insulating material is kept free I from the presence of anyshort-circuiting body, and this is what is meant by the statement thatthe area of the insulating material between the electrodes iscoextensive with the sparking gap or are between the two electrodes.This condition is secured as illustrated in the drawing by reducing orattenuating the inner extremity of the electrode 2, in order that whenthe surrounding electrode 4, is brought into minimum sparking distancewith the former, the entire circumfcrential area of the insulatingmaterial between the two electrodes is such that the flash will beuniform and simultaneous in every radial direction, and hence sparkingcannot take place at any one radial point while shorl-circuitingmaterial may be deposited at some one or more other ,radial localities.

In other words, the extreme diameter of the insulating materialsurroundln the central electrode is coextensive with the sparking gap orare between the electrodes. \Vhile the relation between thetwoelectrodesand the insulating material at the locality where the spark occurs is.designedly such that the spark occurring will be a ring spark andtrend. in all radial directions simultaneously, it will also beunderstood, that this described relation of the electrodes and theinsulating surface is such, that if for any unforeseen reason the sparkshould cease to be a ring-spark, and should travel in a single radialline from the central electrode to the surrounding electrode, andmoisture or other short-circuiting body be deposited upon the insulatingmaterial either side of the sparking ath, the entire superficial area ofthe insu' ation is so limited as not to provide surface sufficient forthe deposited moisture &c. to overcome the natural sparking between theelectrodes. I have taken pains to reiterate this feature of constructionin order that there may be no doubt as to this generic feature of myinvention, as I consider it of the utmost importance. While I prefer toarrange the positive electrode centrally within the insulating materialbetween it and the shell or casing, I desire it to be understood that'Ido not wish to be confined to this particular construction, as thepositive electrode may pass through a surroundin spark gap or opening inthe inner end 0 the shell at any other locality, so long as the relationbetween the electrodes and the body of insulating material is such asdescribed that at the particular locality at which the place, the sparkmust traverse the entire surface of the insulating material and 0perateto keep such surface free from the presence of any short-circuitingmedium.

Having described the construction, op-

eration and advantages of my improved what I claim as new and desire,

spark plug to secure by Letters Patent is:

' insulatin 1. A spark plug embodying in its ora shell having its innerend re-- ganization, turned at an angle to its axis to constitute one ofits electrodes; a second electrode longitudinally disposed within theshell and terminating-in reduced and attenuated form within sparkingdistance from the surrounding returned end of the shell; and a body ofshell an the longitudinally disposed electrode and in contact with thereturned end of the shell and bridging the space between it and thelongitudinally disposed electrode.

2. In a spark plug such as described, a shell returned at its inner endat an angle to its axis, and formed with a perforation or orificetherein; an electrode longitudinally disposed within the shell andterminating in attenuated form, and at sparking distance from theboundary of the perforation or orifice in the returned end of the a bodyof insulating material confined between the shelland the longitudinallydisposed electrode and brid ing the annular space between said electrote and the boundmaterial confined between the shell; and

ary of the perforation or orifice in the returned inner end of theshell, and in substantial contact therewith.

' 3. In a spark plug such shell returned at its inner end at an angle toits axis to constitute one electrode; a second electrode longitudinallydisposed within the shell and terminating in attenuated form, and atsparking distance from the returned inner end of the shell; and aninsulating body of glass occupying the entire space between theshell andthe longitudinally disposed electrode, and Welded to said electrode andshell and'in substantial contact with'theinner end of the latter andbridging the sparking space between the shell and the electrode.

In testimony whereof, I have signed my name to this specification in thepresence of two subscribing witnesses.

. I JAMES C. ANDERSON. Witnesses:

D. G. STUART,

HEnRY C. HAZARD.

as described, a

